My house is over 25 years old and I am looking to have new siding put on my house. I had Amazing Siding come out and give me an estimate and they said they would not tear down the original asbestos siding. They would simply place over it. They said it would be to costly to have it removed. I have some concerns in regards to that.

Wouldn't nailing through the existing shingles cause them to shatter? I think of asbestos being very brittle. Also, how would they know where the studs are when nailing in the new siding?

This is a great question, if it were my house I'd find an installer that is qualified to remove the existing siding and install new. Why? you said it, the hard surface siding will crack underneath. IMO you will get a better install if you start fresh from the substrate. Asbestos removal requires a little extra effort, air quality testing, and wrapping of the old material in plastic and proper disposal at a approved landfill. We usually do a couple of asbestos shingle re-roofs each year, it's really not that much of a problem. We have never spiked the meter on the testing box. You create problems when you make dust and have airborne asbestos particles.

...but its your house, hire a installer who you are comfortable with and check out their references, customers, suppliers and don't pay for the install in full till the jobs complete and you are satisfied with their work. Just my

It is my understanding that as the homeowner, you can remove the asbestos siding yourself and put it out to the curb for trash pickup. However, if your a business that charges for asbestos removal you have to meet certain requirements & licensing.
With that being said, I'd remove the siding myself and then have the contractor come in and install their siding. Possibly install some house wrap and/or foam board prior to installation.

Thanks for the quick replies guys. I will check into the possibility of removing myself. I sure would feel better knowing it was out of there. I'm not real good at fixing things, but I would think it wouldn't be too difficult tearing out the old shingles. Just have to be careful.

The way to do it without breaking the shingles is to clip off the nail heads, and the shingle slides right off. Then bag the nails sideways when you get the insulation board off also, the nails will just snap. Bag the shingles in the appropriate bags, and dispose of usually in the landfill if your town allows it.
talk to your towns rescource director. Otherwise known as the town dump folks.

We have looked into this for our 1900 house. The asbestos siding shingles were placed over the badly weathered original wood siding! We did get an estimate for removal and it was very expensive. I have also been told by siding reps you can go over it. You can pre-drill holes in it by running your drill backwards. However, I'm like you. I'd rather have it all stripped and rewrapped. We repainted for the time being.